Two stage hood lift spring assembly

ABSTRACT

A lift spring assembly has a compression spring rod with a housing having a longitudinal axis and axially opposite ends, and having a rod member coaxial with the axis and having an inner end in the housing and an outer end axially outwardly of one of the opposite ends. A guide member is provided on the inner end of the rod member for supporting the rod member during movement of the rod member. A first stage spring assembly extends between one of the opposite ends of the housing and the guide member. A second stage spring assembly extends between the other of the opposite ends of the housing and the guide member. A mounting member extending from one of the opposite ends of the housing for mounting the spring rod assembly to a hood assembly. A locking member is pivotally connected to the mounting member and pivots into locking engagement with one of the ends of the housing.

This is a divisional application of U.S. application Ser. No.10/631,514, filed Jul. 31, 2003 now U.S. Pat. No. 7,261,286.

BACKGROUND OF THE INVENTION

The invention relates to a spring mechanism typically used for biasinghoods, tops, doors, hinged covers, and other elements from a closed toan open position. The invention involves the use of springs inconjunction with a rod member to exert a driving force on the elementsto be displaced. The following patents are incorporated herein byreference as background information with regard to spring mechanisms:U.S. Pat. No. 6,199,843 to DeGrace; U.S. Pat. No. 5,810,339 to Küspert,et al.; and U.S. Pat. No. 4,962,916 to Palinkas.

Compression spring rods are used in various applications; for example,to assist in lifting, opening, and damping. Typical applications includelifting a lid hinged to a stationary base. Other applications includelifting and/or balancing elements for a trunk or hood of an automobile.The present invention uses the compression spring rod assembly to assista hood of a bus during opening of the hood and securing the hood inplace in a fully opened position. A two stage spring assembly is used inwhich the first stage spring assists during the opening process and thesecond stage spring assembly is used to prevent the hood from fallingafter passing a center of gravity point of the hood.

Existing mechanical lifts for bus hoods, such as for school busses, usea combination of extension springs and cable for assisting opening andclosing of the bus hoods. The force needed to open a school bus hood istypically required to be less than 25 lbs. The existing systems havedifficulty meeting this requirement. In contrast, the two stage springassembly of the present invention only requires approximately 15 lbs. ofhandle load to open the hood. The system assists the hood in opening,and slows the hood as it approaches the end of the stroke and limits thetravel of the hood. Accordingly, it is considered desirable to provide anew and improved two stage spring assembly which overcomes the foregoingdifficulties and others while providing better and more advantageousresults.

Typically, bus hoods are oriented such that the top of the hood isessentially parallel to the ground thus providing the driver with alimited line of vision with respect to objects or persons in front ofthe bus. An improved bus hood design provides a downward angle or slopeto the top of the hood from the windshield thus providing increasedvisibility to the area in front of the bus. Thus, the driver has abetter view of either objects or children or persons walking in front ofor positioned in front of the bus. Thus, the slant or slope design ofthe hood increases the safety to people around the bus while the bus iseither stationary or in transit.

The hood is lifted away from the windshield towards the front of thebus. Once the hood passes a vertical position balanced with respect toits center of gravity, it tends to drop or fall due to gravity and mayinjure the person opening the hood. Thus, a two stage spring assembly isdesired for controlling movement of the hood before and after it reachesa vertical position balanced at its center of gravity.

SUMMARY OF THE INVENTION

The present invention provides an improved compression spring rodassembly which overcomes the above referred-to difficulties and otherswith regard to such assemblies heretofore available. The compressionspring rod assembly utilizes a two stage spring assembly to provide aconstant and controlled force to assist in opening of a bus hood untilit is positioned over a center of gravity and then a second spring isprovided to cushion and limit travel of the hood past the center ofgravity so that the hood's movement is slowed or limited and the personopening the hood is not injured.

More particularly, the invention relates to a lift spring assembly,comprising a compression spring rod with a housing having a longitudinalaxis and axially opposite ends and a rod member coaxial with the axisand having an inner end in the housing and an outer end axiallyoutwardly of one of the opposite ends and a guide member on the innerend of the rod member for supporting it during movement.

A first spring assembly extends between one of the opposite ends of thehousing and the guide member. A second spring assembly extends betweenthe other of the opposite ends of the housing and the guide member. Amounting member extends from one of the opposite ends of the housing formounting the spring rod assembly to an associated hood assembly. Alocking member is pivotally connected to the mounting member and extendsalong a longitudinal axis of the housing. The locking member pivots intolocking engagement with one of the ends of the housing.

In accordance with another aspect of the present invention, a two stagehood lift assembly comprises a hood pivotably mounted to an associatedvehicle and a compression spring rod assembly. The spring rod assemblycomprises a housing having a longitudinal axis and axially oppositeends, and a rod member coaxial with the axis and having an inner end inthe housing and an outer end axially outwardly of one of the oppositeends.

A first stage spring assembly extends along the longitudinal axis of thehousing. A second stage spring assembly extends between an end of thefirst stage spring assembly and an end of the housing.

A mounting member is connected to the outer end of the rod member, andsecures the compression rod assembly to the hood. A latch is pivotallyconnected to the outer end of the member and extends along alongitudinal axis of the housing.

In accordance with yet another aspect of the present invention, a hoodlift spring assembly comprises a compression spring rod assemblycomprising a housing having a longitudinal axis and axially oppositeends, a rod member coaxial with the axis and having an inner end in thehousing and an outer end axially outwardly of one of the opposite endsand a guide member on the inner end of the rod member for supporting itduring movement.

A first spring assembly extends between one of the ends of the housingand the guide member, and the second spring assembly extends between theguide member and the other of the ends of the housing. A latch membercomprises a spring biased clip attached to an end of the housing,wherein the clip engages a notch within the rod member when the rodmember is in an extended position.

The two stage spring assembly has a first stage comprised of severalsprings stacked on top of each other in series to allow a long travel ofthe hood in the initial opening process. The first spring assembly maycomprise several springs in series or several springs including a centerspring positioned or interleaved within the other springs. A secondstage spring which may comprise one or two springs acts as a cushion toslow down travel of the hood after it passes over a center of gravityposition. The hood would normally begin falling quickly once it passesthe center of gravity position and potentially injure a person openingthe hood. A latch or clip is used to secure the hood in the fully openedposition and prevent it from swinging back to a closed position withoutfirst disengaging the latch or clip.

The compression spring rod assembly includes a rod which is adapted toextend and retract relative to a housing. In a typical application, thecompression spring builds potential force as the springs are compressedand releases that force once the springs are allowed to expand. Thisextension of the springs imparts a force to the part connected to theends of the rod housing and, advantageously, multiple end configurationscan be used to adapt the spring rod to a variety of applications. Theencased springs minimize load losses over time and do not contain anyfluid or gasses within the body. This advantageously eliminates theinevitable problem of leakage and loss of utility.

The second stage spring assembly, which serves as a cushion, comprises asingle spring or multiple springs which remain in an extended andrelaxed position until the first spring assembly is fully extended, thenthe spring(s) are compressed due to contact with a guide member or thepiston and cushion or slow the travel of the hood once it passes thecenter of gravity position. As the rod travels during the openingprocess, a latch moves along with the rod until the hood is fully openedand the second spring assembly begins to be compressed. The latch thenfalls against an end member of the second spring assembly and preventsmovement of the hood backwards to the initial closed position. The latchis manually moved or lifted out of engagement with the end of the springrod assembly to allow the rod to travel back through the spring housingand allow the hood to be returned to the closed position. Alternatively,a spring loaded latch or clip is positioned on the end of the spring rodhousing and engages a notch in the spring rod in the fully openedposition. The notch allows for a slight amount of extra travel by therod until the clip enters the notch and prevents the hood from returningback to the closed position. The spring loaded clip prevents furthertravel in the forward or backward direction. The spring loaded clip ismanually depressed to disengage the clip from the notch and allow thehood and spring rod to travel in the opposite direction and allow thehood to return to a closed configuration.

It is accordingly an object of the present invention to provide animproved compression spring rod assembly with one or more springs forexerting an operating force on a displaceable member at a controlledrate.

Another object of the invention is the provision of a compression springrod having at least two compression springs interrelated to minimizeload losses over time.

A further object of the invention is to provide a two stage compressionspring assembly having a first stage spring for assisting opening of ahood and a second stage spring to cushion or slow movement of the hoodafter it passes a center of gravity position.

A further object of the invention is to provide a latching mechanismwhich prevents the hood from returning to a closed position after it isextended to the fully opened position.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects and advantages will in part be obviousand in part pointed out in the following description taken together withthe accompanying drawings in which:

FIG. 1 shows a side elevation view of a vehicle hood and a compressionspring rod, shown in dotted lines, in a fully closed position accordingto a preferred embodiment of the present invention;

FIG. 2 is a side elevational view of the vehicle hood and thecompression spring rod assembly of FIG. 1 where the hood is in abalanced position over the center of gravity of the hood;

FIG. 3 is a side elevational view of the vehicle hood and compressionspring rod assembly of FIG. 1 in which the hood is in a fully openedposition;

FIG. 4 is a plan view of a two stage compression spring rod assembly,shown partially in dotted lines, in the fully closed position of FIG. 1;

FIG. 5 shows the compression spring rod assembly in a fully collapsedposition shown in partial cross section;

FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. 5illustrating a latch mechanism and a mount on the hood in which thespring rod assembly is mounted;

FIG. 7 a is a schematic illustration of the two stage compression rodassembly in which the first spring assembly is in the collapsed positionand the second spring assembly is in a relaxed uncompressedconfiguration corresponding to FIG. 1;

FIG. 7 b is a schematic illustration of the two stage compression springrod assembly in which the first stage spring assembly is extended andthe hood is balancing over the center of gravity and the second springassembly is in an uncompressed condition corresponding to FIG. 2;

FIG. 7 c is a schematic illustration of the first stage compressionspring rod assembly in an extended uncompressed condition and the secondstage spring assembly in a compressed configuration with the latchengaging the end of the rod assembly to prevent further backward travelof the rod corresponding to FIG. 3;

FIG. 8 illustrates an alternate spring loaded clip mechanism forsecuring the spring rod in the fully extended position to preventbackward or forward travel of the rod;

FIG. 9 illustrates an alternate embodiment of the present invention inwhich the first stage compression spring has two outer springs and ancentral inner spring; and

FIG. 10 illustrates an alternate embodiment of the present invention inwhich the second stage compression spring has a outer and an innerspring interleaved with one another.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

Referring now in greater detail to the drawings, wherein the showingsare for the purpose of illustrating preferred embodiments of theinvention only, and not for the purpose of limiting the invention, FIG.1 shows a front section of a vehicle A, such as a school bus, with adownwardly sloped or angled hood B pivotally connected to the school bushaving a compression spring rod assembly C attached thereto. The hood Bis downwardly sloped or angled with respect to the windshield to providea greater line of vision for the school bus driver. The driver then hasan increased line of visibility with respect to objects or persons infront of the bus. FIG. 1 illustrates the hood and compression spring rodassembly in the fully closed and secured position.

FIG. 2 illustrates the hood B and compression rod assembly C where thehood is balanced over the center of gravity of the hood. The hood wouldthen have a tendency to continue travelling in the right hand directionas illustrated by the arrow past the center of gravity to a fully openedposition. If the hood's travel is not limited or cushioned, the hoodcould potentially injure the person who is manually opening the hood.When the hood is in the balanced position over its center of gravity, itis approximately 45 or 46 degrees from vertical.

Referring now to FIG. 3, the hood is shown in the fully opened positionpast the center of gravity in which the compression rod assembly hascushioned the travel of the hood and has a latch which prevents furthermovement back toward the closed position. In the fully opened positionthe hood is positioned at about 68 degrees from vertical.

Referring now to FIGS. 4 and 5, a two stage spring assembly isillustrated which utilizes a first stage spring which is used to open ahood and a second stage spring which is used to prevent the hood fromfalling after passing a center of gravity point of the hood. Thecompression spring rod assembly C has a compression spring rod 10 withan axis 11 and a rod member 22 which is axially extendable andretractable relative to a one-piece tubular housing 24. The housing 24has a longitudinal axis and axially opposite ends. Rod 22 has an outerend 22 a axially outwardly of one of the opposite ends of the housingand an inner end 22 b. In this embodiment, three compression springs 28,29, 30 are stacked one on top of the other and are positioned in serieswith respect to each other. Compression springs 28, 29, 30 form thefirst stage spring assembly. The compression springs are supportedagainst buckling by interior surface 48 of housing 24. Housing 24 has amounting end 23 and an outer opposite end 25, and compression springs28, 29, 30 are axially captured between a tail bushing 38 at mountingend 23 and a guide member or plug 34 mounted at inner end 22 b of rod22. The compression springs 28, 29, 30 bias the rod member toward anextended position of the rod member.

Compression spring rod 10 involves the use of a one-piece housing 24which facilitates smooth movement of rod 22 and compression springs 28,29, 30 during operation of the spring rod. Tail bushing 38 has athreaded stud 44 which is received in a threaded recess 17 in a mountingelement 18. Rod 22 includes a threaded stud 52 which passes through anopening 58 of guide member 34 and into a threaded bore 54 provided inthe rod 22. Lift rod 22 passes through an opening 72 through a rodbushing 73 at outer end 25 of housing 24, and has a threaded stud 70 onouter end 22 a thereof which is received in a threaded recess 27provided in a mounting element 20.

Mounting elements 18 and 20 have openings 19 and 21 therethrough forreceiving a variety of different mounting components common in theindustry including, for example, pins, bolts, swivels, and the like. Thethreaded studs 44 and 70 at opposite ends of the spring rod assemblyprovide for accommodating the use of different mounting elements thanthose shown so as to modify the assembly for use in a variety ofstructural environments.

Guide member or plug 34 is slidable in the housing 24 and includes aguide ring of suitable material to facilitate such sliding movement. Rod22 is slidably supported at end 25 of housing 24 by rod bushing 73 andcan be secured to the housing by a pair of set screws or other suitablefasteners having inner ends received in an annular recess in the rodbushing. Referring to FIG. 5, rod 22 has a stepped portion 35 whichserves as a stop to prevent overtravel of the rod and potential loaddamage. Guide member 34 and the rod bushing support the rod 22 forreciprocation in housing 24 between extended and retracted positions tomaintain minimal breakaway forces for rod 22. Additionally, guide member34 and the rod bushing keep rod 22 coaxial with axis 11 and decrease theeffect of sideloading on the assembly.

The compression spring rod 10 through the spring-like characteristics ofthe compression springs 28, 29, 30 serves to provide smooth extensionforces to the movement of lift rod 22 from a retracted to an extendedposition thereof relative to housing 24. Depending on the application,the appropriate load versus deflection can be determined and thecorresponding physical elastic properties of the combination ofcompression springs 28, 29, 30 can then be ascertained. Each compressionspring can be fabricated from spring material, such as music wire, andfor example ASTM A228 or 302 stainless steel. The springs are capturedbetween bushing 38 and plug 34. FIGS. 4 and 5 illustrate the first stagespring assembly in the compressed configuration.

Referring now to FIG. 5, a second stage spring assembly which is used tocushion the movement of the hood to the fully opened position, includesa single spring 31 which is positioned between guide plug 34 and bushing73. As seen in FIG. 5, spring 31 is in the fully relaxed and extendedposition. FIGS. 5 and 6 also show a latch or locking member 33 which ispivotally connected to mounting element 40 via a bushing or collar 42 ona threaded fastener 41 which extends from the mounting element 40 to amounting element 20 of the rod and spring assembly. The mounting element40 mounts the spring rod assembly to a hood assembly. The latch can befabricated from metal or another suitable material and is shown in FIG.5 to be an angled metal bar. The latch 33 includes a first arm 96 havingan opening 97 therein for pivotably mounting the latch onto mountingelement 40 via a fastener or other suitable means. A second arm 98extends from and is approximately perpendicular to the first arm. Eachof the arms has a first end 99, 101 and a second end 102, 100,respectively. The first ends are pivotally attached at an end of the rodmember extending beyond an end of the housing. The latch extends along alongitudinal axis of the housing. A threaded stud extends through themounting element 40 and secures the compression spring rod and latch inposition with respect to the mounting element 40. The latch is used topivot into locking engagement with an end of the housing.

Referring now to FIGS. 7 a-7 c, a compression spring rod two stageassembly is schematically illustrated in the fully closed, partiallyopened and fully opened positions. Referring first to FIG. 7 a, thefirst stage compression spring assembly which comprises springs 28, 29,30 is shown to be in the compressed configuration. Second stage springassembly 31 is shown to be in the fully extended or relaxed position.This configuration of the spring rod assembly corresponds to the hood inthe fully closed position as shown in FIG. 1. As the hood is opened asillustrated in FIG. 2, the compression spring first stage springassembly extends as shown in FIG. 7 b until the hood is in the balancedposition over its center of gravity. At this point, the second stagespring is still not contacting the guide plug or piston 34. The firststage spring assembly is still in a compressed state. Rod 22 extends outof the housing 24 and the latch 33 also is pulled along with the rod asseen in FIG. 7 b. As soon as the hood extends past the center ofgravity, gravity would tend to pull the hood downwardly and cause it todrop or fall in a rapid manner. To avoid this, the second stage spring31 begins to be compressed by the guide plug 34 as seen in FIG. 7 c,thus slowing down the speed of movement of the hood to the fully openedposition. In this configuration, the first stage spring assembly is in afully extended position. The latch extends further with rod 22 until itdrops into engagement with the outer end of the housing at the bushing73. The end 100 of the second arm of the latch then contacts the bushingas seen in FIG. 7 c thus preventing backward movement or movement of thehood back to a closed position. The latch has to be manually disengagedfrom the end of the bushing and is placed onto the outward edge of thehousing 24 to allow the backward travel of the hood from the fullyopened position to a fully closed or partially closed position. Thelatch rides along the outside edge of the housing as the rod moves intothe housing.

Referring to FIG. 8, an alternate embodiment of a latching mechanism isillustrated. The compression spring rod assembly is substantially asdescribed for FIGS. 4, 5 and 7. A spring loaded clip or latch 50includes a first arm 52 and a second arm 54 which is pivotally attachedto the end of the housing through a mounting member 56. Spring 58extends between a notch 60 of arm 52 and a notch 62 of mounting plate 64positioned on an end of the rod housing. The spring is biased so thatthe clip arm 54 hangs or extends downwardly as seen in FIG. 8. A notch66 is formed in rod 22 to secure the rod in the fully opened position.The notch is slightly larger than the end dimension of the arm 54 toprovide for slight misalignment between the arm 54 and rod 22 or if therod and hood need to be slightly pulled further to be secured in thefully opened position. The clip arm 54 drops or falls into notch 66 whenthe rod is in an extended position thus preventing the rod from furthertraveling forward or backward to a closed position of the hood. Torelease the clip from the notch, the arm 52 is manually depressed, thuscompressing spring 62 and raising or lifting the arm 54 out ofengagement with notch 66.

FIG. 9 illustrates an alternate embodiment of the compression spring rodassembly. Like components to those illustrated in FIGS. 4 and 5 arelabeled with numerals with a prime (′). In this embodiment, the firststage compression spring comprises two outer springs 80, 82 and acentral, inner spring 84 which is oppositely wound to springs 80, 82.The inner spring is provided to provide greater strength in the springassembly to provide greater resistance to closing the hood. The secondstage spring assembly is a single spring 31′ as is shown for theembodiment of FIGS. 1-5.

Another alternate embodiment is illustrated in FIG. 10. Like componentsto those illustrated in FIGS. 4 and 5 are labeled with numerals with adouble prime (″). In this embodiment, the first stage compression springis a single continuous spring 90 and the second stage spring assemblycomprises an outer spring 92 and an inner oppositely wound spring 94. Inthis configuration, the inner spring on the second stage spring assemblyprovides greater strength and resistance to the hood being opened pastthe center of gravity to the fully opened position.

While considerable emphasis has been placed herein on the structures andconfigurations of the preferred embodiments of the invention, it will beappreciated that other embodiments, as well as modifications of theembodiments disclosed herein, can be made without departing from theprinciples in the invention. In this respect, it will be appreciatedthat the spring rod can be used in applications other than thosedisclosed herein. Similarly, multiple combinations of coaxial andsurrounding springs (i.e., 3, 4, etc.) may be configured to meet thedesired load vs. deflections for a particular application. Likewise, itwill be appreciated that the spring rod according to the invention canbe secured to relatively displaceable components in any number ofdifferent ways. Furthermore, the use of a compression spring rod and thelatching mechanisms described hereinabove can be used in otherapplications beyond a bus hood. These and other modifications of thepreferred embodiments, as well as other embodiments of the invention,will be obvious and suggested to those skilled in the art from thedisclosure herein, whereby it is to be distinctly understood that theforegoing descriptive matter is to be interpreted merely as illustrativeof the present invention and not as a limitation thereof.

1. A hood lift spring assembly comprising: a compression spring rodassembly comprising a housing having a longitudinal axis and axiallyopposite ends; a mounting element for securing said compression springrod assembly to an associated hood; a horizontal rod member coaxial withsaid axis and having an inner end in said housing and an outer endaxially outwardly of one of said opposite ends; a guide member on saidinner end of said rod member for supporting said rod member duringmovement of said rod member; first and second spring assemblies, whereinsaid first spring assembly extends between one of said ends of saidhousing and said guide member, and said second spring assembly extendsbetween said guide member and said other of said ends of said housing;and a spring biased latch comprising a clip pivotally attached to an endof said housing via a mounting member, wherein said clip comprises aspring which is received in an elongated notch within a mounting plateon said housing and an elongated notch within a first arm of said clipwherein said spring extends vertically between said elongated notch ofsaid mounting plate and said elongated notch of said first arm of saidclip; wherein said mounting plate is spaced from said first arm, and anL-shaped second arm of said clip comprising a first member substantiallyparallel to said horizontal rod member; and a second member which isperpendicular to said first member; wherein said second member and saidspring are substantially parallel to each other; wherein said secondmember moves downwardly to engage a notch within said horizontal rodmember when said rod member is in an extended position, wherein saidnotch in said rod member is larger in dimension than said second memberof said second arm of said clip to provide for misalignment of saidsecond arm and said rod.
 2. The hood lift spring assembly of claim 1,wherein said first arm is manually depressed to release said second armfrom engagement with said notch in said rod member.
 3. The hood liftspring assembly of claim 1, further comprising a bushing adjacent saidone of said opposite ends of said housing supporting said rod member forreciprocation axially of said housing between extended and retractedpositions relative thereto.
 4. The hood lift spring assembly of claim 1,wherein said first spring assembly comprises three springs adjacent eachother in a stacked relationship.
 5. The hood lift spring assembly ofclaim 1, wherein said first spring assembly is in a compressedconfiguration when said associated hood is in a closed position.
 6. Thehood lift spring assembly of claim 1, wherein said second springassembly is in an extended position when said associated hood is in aclosed position.
 7. The hood lift spring assembly of claim 3, whereinsaid first spring assembly extends between said guide member and saidbushing coaxial with said axis for biasing said rod member toward theextended position thereof.
 8. The hood lift spring assembly of claim 1,wherein said first spring assembly is in a fully extended position andsaid second spring assembly is in a compressed position when saidassociated hood is in a fully opened position.
 9. The hood lift springassembly of claim 3, wherein said first spring assembly is partiallycompressed and said second spring assembly engages said bushing of saidrod assembly as the associated hood is balanced over its center ofgravity.
 10. The hood lift spring assembly of claim 1, wherein saidfirst spring assembly comprises first and second outer springs and aninner spring positioned within said outer springs.
 11. The hood liftspring assembly of claim 10, wherein said inner spring is oppositelywound to said outer springs.
 12. The hood lift spring assembly of claim1, wherein said first spring assembly comprises a single continuousspring.
 13. The hood lift spring assembly of claim 12, wherein saidsecond spring assembly comprises a first outer spring and a second innerspring positioned within said outer spring.
 14. The hood lift springassembly of claim 13, wherein said second inner spring is oppositelywound from said first outer spring.